1. Field of the Invention
This disclosure relates to a semiconductor memory device, and more particularly, to a fin field effect transistor where a fin type active region is formed.
2. Description of the Related Art
Recently continuous requirements for semiconductor memory devices having lower power consumption, higher efficiency, and improved speed operation characteristics have brought about a continuously reduced design rule for the purposes of integrating more semiconductor memory devices within a semiconductor chip of a limited size. However, as semiconductor memory devices become increasingly integrated, the channel length of individual devices is gradually reduced. This causes a short channel effect, increases the channel doping density of transistors constituting a memory cell, and also increases the junction leakage current.
To solve these problems, fin field effect transistors (fin FETs) that have a fin-type active region are formed on an SOI (Silicon On Insulator) silicon substrate and then a gate electrode is formed on the fin region. An example of such a device is disclosed in U.S. Pat. No. 6,525,403 entitled “Semiconductor device having MIS field effect transistors or three-dimensional structure”.
Such a fin FET can effectively control a leakage current generated in a channel and can ensure a channel length, preventing or substantially reducing a short channel effect and improving swing characteristics of the transistor and decreasing a leakage current. However, there are still some disadvantages that exist when the fin FET is formed on the SOI silicon substrate because the price of SOI wafers is higher than bulk wafers and the parasitic source/drain resistance increases. Furthermore, a channel formation body of the semiconductor device is not connected to the SOI substrate according to a characteristic of the SOI device, thus a floating body effect is present, and heat generated in the device that is typically conducted to the SOI silicon substrate is cut off by an oxide layer formed on the SOI silicon substrate, thus degrading the performance of the semiconductor device.
Embodiments of the invention address these and other disadvantages of the conventional art.